The present invention relates to apparatus for testing plain or filter-tipped cigarettes, cigars, cigarillos, filter rod sections and analogous rod-shaped articles of the tobacco processing industry. More particularly, the invention relates to improvements in pneumatic testing apparatus for such rod-shaped articles. Still more particularly, the invention relates to improvements in apparatus for influencing the gaseous testing fluid which is supplied to pneumatic testing devices for cigarettes or the like.
It is already known to install a pressure regulating system in the conduit which supplies gaseous testing fluid from a suitable source to the testing device for cigarettes or like rod-shaped articles of the tobacco processing industry. It is further known to install in the conduit a vessel whose volume is such that it can store a substantial quantity of testing fluid, namely, a quantity which is a multiple of the quantity of testing fluid that is required for the testing of a single rod-shaped article. The vessel has an inlet which receives testing fluid from the pressure regulating system and an outlet which admits testing fluid to the testing device.
The requirements concerning the accuracy of conditioning the testing fluid prior to admission of conditioned fluid into the testing device depend on the desired degree of accuracy of the testing operation. Thus, the pressure of testing fluid must be stabilized with a very high degree of accuracy if the testing device is to test the rod-shaped articles with a view to ascertain small or minute deviations of the characteristics of such articles from an optimum value. This is the case when the testing device is to monitor the permeability of intentionally perforated portions of the wrappers of plain or filter cigarettes. The purpose of such perforated portions is to admit predetermined quantities of cool atmospheric air into the column of tobacco smoke. Cool atmospheric air is believed to exert a desirable influence upon the percentage of nicotine and condensate in tobacco smoke. The making of perforations involves burning holes into the wrappers (e.g., by resorting to a laser or by causing the web of cigarette paper or other wrapping material to advance through the gaps between a series of electrodes) or the making of holes with resort to needles or the like. Reference may be had to commonly owned U.S. Pat. No. 4,121,595 granted Oct. 24, 1978 to Uwe Heitmann et al. and to commonly owned U.S. Pat. No. 4,281,670 granted Aug. 4, 1981 to Uwe Heitmann et al. for apparatus which perforate a web of wrapping material with one or more laser beams, to commonly owned U.S. Pat. No. 4,247,754 granted Jan. 27, 1981 to Anton Baier for apparatus which perforates a web of wrapping material by sparks during travel of the web between several electrodes, and to commonly owned U.S. Pat. No. 4,090,826 granted May 23, 1978 to Alfred Hinzmann for apparatus which serves to make perforations by mechanical means.
As the sensitivity of the testing device increases, it is necessary to supply to such device a stream of testing fluid whose pressure fluctuates very little or not at all. The perforations in the wrappers of cigarettes or the like are very small so that their detection necessitates resort to highly sensitive testing devices. Presently known testing devices which are used for such purposes react very unfavorably to any, even minor, fluctuations of the pressure of testing fluid which is delivered thereto for the purpose of testing each of a series of successive rod-shaped articles. Any fluctuations of the pressure of admitted testing fluid distort the results of measurements and are likely to lead to ejection of satisfactory articles and/or to retention of unsatisfactory articles.
U.S. Pat. No. 3,426,582 discloses a pressure stabilizing apparatus of the above outlined character which is designed to prevent fluctuations of the pressure of testing fluid from affecting the operation of the testing device proper. German Offenlegungsschrift No. 2,234,094 discloses an apparatus which provides an outlet serving to allow for regulation of the pressure of testing fluid which is admitted to the testing device. A drawback of the just discussed prior apparatus is that they cannot compensate for those fluctuations of the pressure of testing fluid which are attributable to the testing device, especially fluctuations which are attributable to occasional absence of rod-shaped articles at the testing station due to ejection of defective articles ahead of the testing station or which are attributable to the testing of highly defective articles with open seams, large holes, etc. In the absence of a cigarette at the testing station while the testing device discharges testing fluid in anticipation of the presence of an article at the testing station, the testing device discharages a substantial amount of testing fluid which can affect the pressure of fluid that is held in a state of readiness for the next testing operation. Therefore, the testing of the next-following article is not likely to be satisfactory or, if satisfactory for the detection of pronounced defects (such as fully open seams or large holes), is not sufficiently accurate to detect deviations of permeability of the aforediscussed intentionally produced perforations from an optimum permeability.